This invention generally relates to probes for aspirating and dispensing fluids, and more particularly to probes for typical use in pipetting multiple liquids in laboratory analysis processes.
In modern laboratory analysis, for example analysis of blood serums, large numbers of serum samples, controls and other reagents must be processed in high speed, automatic equipment; such equipment is described in copending U.S. patent application Ser. No. 115,734, filed Jan. 28, 1980 in the names Ginsberg et al, entitled System and Probe for Chemical Reaction Observation With A Moving Photometer, which application is now allowed and is incorporated herein by reference. Such instruments can perform highly accurate determinations, but a recurring problem arises in cross-contamination between various specimens. Where a number of specimens are to be withdrawn from different containers and placed in analysis vessels, it is necessary that substantially no portion of the specimen taken from one container be introduced into another or different container. This contamination occurs commonly when a pipette, or probe, is used to aspirate or withdraw a multiple specimens, reagents, and other liquids; often, excess liquid adheres to the tip of the pipette probe which is immersed in a specimen or reagent for transfer of a portion to an analysis vessel, with the adhering excess liquid causing contamination of a succeeding specimen aspirated into the same probe.
Attempts made in the prior art to reduce the contamination problem have included rinsing of the transfer probe, however, such rinsing can draw some of the liquid sample from the tip, reducing volumetric accuracy. Use of compressed air to dry the tip may also tend to disturb the liquid in the interior of the tip causing droplets to be blown from the tip.
While many types of needlepoint probes have been developed such as those marketed by the Hamilton Company, no tip design has successfully eliminated drops from adhering to the exterior of the tip.